1. Field of the Invention
The present invention relates to a Micro Electro Mechanical System (MEMS) switch and a manufacturing method thereof.
2. Description of the Related Art
Electronic systems used at a high frequency band are becoming ultra-compact, ultra-light and better in performance. Accordingly, in the existing electronic system, researches are ongoing on a micro switch using a new technology called a micromachining as a substitute for a semiconductor switch such as an FET (Field Effect Transistor) or a PIN diode.
The most widely manufactured device out of Radio Frequency (RF) devices using the MEMS technology is a switch.
The RF switch is a device widely applied for selective transmission of signals and impedance matching circuits in wireless communication terminals of microwave or millimeter wave bands and systems thereof.
FIG. 1 is a side view illustrating structure of a seesaw type MEMS switch according to the prior art, and FIGS. 2A and 2B are operational constitutional representations illustrating a state where the switch of FIG. 1 is operating.
Referring to FIG. 1, a conventional MEMS switch 1 is disposed in a seesaw-like structure at a top of a substrate 2, spaced a predetermined distance apart, with a movable electrode 3 via a spring arm 5.
The movable electrode 3 is formed at least one end thereof with a contact member 7, and a signal line 9 is formed on top of the substrate 2 with respect to a location opposite to the contact member 7.
A fixed electrode 11 is formed on top of the substrate 2 for generating an electrostatic force along with the movable electrode 3 and for contacting the contact member 7 to the signal line 9, and the other end of the fixed electrode 11 is formed with a restoring electrode 13 for distancing one end of the movable electrode 3 provided with the contact member 7 from the substrate 2.
Referring to FIG. 2A, if a voltage is applied to the fixed electrode 11 in the conventional MEMS switch 1, an electric charge is generated therebetween, and the movable electrode 3 is rotated clockwise about the spring arm 5 by the electrostatic force to cause the contact member 7 provided at the bottom of the movable electrode 3 to contact the signal line 9.
Referring now to FIG. 2B, if a voltage is applied to the restoring electrode 13 by releasing the voltage of the fixed electrode 11, the movable electrode 3 is rotated counterclockwise about the spring arm 5 to cause the contact member 7 to distance from the signal line 9.
The seesaw-type MEMS switch thus described has an advantage in that the restoring force can be increased by embodying on a same planar surface a restoring part using the electrostatic force for easy MEMS process, in addition to the restoring force by a mechanical spring compared with an existing planar type switch (a membrane type where the entire movable electrode is fixed with respect to the substrate).
However, there is a disadvantage in that, because the movable electrode 3 is inclined at a predetermined degree (θ°) as illustrated in FIG. 2A when the contact member 7 contacts the signal line 9, the contact force of the contact member 7 becomes relatively decreased due to inefficiency of electrode gap with respect to planar type, resulting in increase of driving voltage.
There is another disadvantage in that when the contact member 7 and the signal line 9 are brought into contact, a distance (L) from the substrate 2 to an opposite end of the contact member 7 is lengthened, resulting in increase of the restoring voltage for restoring the movable electrode 3.